If the tyre causes either damage to the road, or to persons, or to any vehicle using the road. This would cover such instances as if a vehicle with damaged or very oversized tyres which either caught against a person or other vehicle resulting in either damage or injury. Studded tyres also are included in this clause and if used in inappropriate conditions (i.e. where there is no ice or snow) and they damage the road surface then they would be clearly illegal.